I am working in Netbeans on Ubuntu for the last 4 months. But today when I opened Netbeans, it just got stuck in the Ubuntu launcher bar at the left side of screen.

I have my project pending in Netbeans (which is not opening). I am stuck in this problem.
I also rebooted Ubuntu a number of times, still the same. I can't open Netbeans.
Why is this happening? What is the cause of this problem? What should I do?

tried $gksu netbeans, nothing happens, $ prompt shown again.